Fans and fan systems have had a variety of components and have come in a variety of configurations over the years. In the construction of vertical-shaft ceiling fans, it may be common to provide a central passage through the motor, through which wiring may be passed to provide power connections to a lamp or other accessory that may be attached below the center of the fan. For this purpose, in some situations, it may be important that the central passage, as well as the point of attachment for the lamp or accessory itself, remain stationary as the blades of the fan rotate about it. One method of construction to provide this feature may be to construct the motor with the stationary component (e.g., the stator, etc.), including the power connections and windings, in the center; and with the rotating component (e.g., the rotor, etc.), which does not contain windings or power connections, configured as a shell surrounding the stationary center component. In this construction, the provision of a stationary passage through the center may be a simple matter of forming a vertical hole through the center of the stationary motor component.
While this method of construction may be successful in relatively small fans with low-power motors, it may become impractical when the fan (and its corresponding power requirement) becomes larger, because the isolation of the heat-producing motor windings in the center of the assembly may prevent adequate heat dissipation to control the temperature of the motor windings. In some settings with these higher power applications, a conventional motor (e.g., with stationary windings on the outside and a rotating core in the center) may be more desirable, either alone or in conjunction with a speed-reducing gear box interposed between the motor and the fan hub.
In some situations, it may or may not be desirable to have a fan react in some way when there is a fire in the structure in which the fan is located. For instance, some High Volume/Low Speed fans may be large in size (e.g., between 8 and 24 feet in diameter, etc.), may move a substantial volume of air (e.g., 300,000 cubic feet or more per minute, etc.), and may be mounted as ceiling fans, hanging below the roof structure of a building. As such, in certain circumstances, it may be desirable for such a fan to be stopped from operating in the event of a fire in a building. In addition, the underside of the fan being suspended some distance below the roof may be a desirable location in which to place a fire and/or smoke detection sensor, as this location being closer to the source of a fire and/or smoke may provide an earlier detection than would result from the sensor being located at the ceiling level.
Furthermore, in some situations, it may or may not be desirable to have a fan react in some way when a component of the fan impacts an object and/or when there is an imbalance in the fan system. For instance, as noted above, some High Volume/Low Speed fans may be large in size (e.g., between 8 and 24 feet in diameter, etc.), and may be mounted as ceiling fans, hanging below the roof structure of a building. In this location, in some situations, it may be possible on occasion for a fan blade to strike an obstruction such as the raised fork structure of a fork lift. It may also be possible for a fan assembly to become out of balance due to some other cause such as an object falling onto a blade or a foreign material accumulating on a blade. In any of these situations or other situations, it may be desirable for the fan to be automatically be brought to a stop or slow down so that it will not continue to operate in an unstable or out of balance condition that might otherwise result in damage to the fan or to the surroundings.
While fans and fan systems have had a variety of components and configurations, and while fans and fan systems have been operated in a variety of ways, it is believed that no one prior to the inventors has made or used the invention recited in the appended claims.
Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings. To the extent that specific dimensions are shown in the accompanying drawings, such dimensions should be regarded as merely illustrative and not limiting in any way. Accordingly, it will be appreciated that such dimensions may be varied in any suitable way.